I have a SquareD Homeline HOM3040M200TC (30 circuits, 10 tandems, 40 total). I'd like to install a 100A sub-panel in my garage which currently has no power, I'll be running the line myself from the house which is about 150ft.

The service line is 200A, and I've counted up 260A worth of circuits in my main panel. What does this mean exactly in terms of my limitations?

It's going to be used to put some lights in the garage, a door opener and will be used with tools such as a circular saw/jigsaw/etc. Eventually I'll get a compressor but none of these should be on at the same time - save the lights.

I have a SquareD Homeline HOM3040M200TC (30 circuits, 10 tandems, 40 total). I'd like to install a 100A sub-panel in my garage which currently has no power, I'll be running the line myself from the house which is about 150ft.

The service line is 200A, and I've counted up 260A worth of circuits in my main panel. What does this mean exactly in terms of my limitations?

200 amps means 200 amps per leg and you have 2 legs of power, so that's 400 amps. If you have a 200 amp breaker , you can use up to 80% of that so that's 160 amps per leg. two legs would be 320 amps.
If you added up 260 amps of breakers and you can use 80% of that , that would be 208. 320- 208 still leaves you 112. So it looks like you are in good shape. Paul

200 amps means 200 amps per leg and you have 2 legs of power, so that's 400 amps. If you have a 200 amp breaker , you can use up to 80% of that so that's 160 amps per leg. two legs would be 320 amps. If you added up 260 amps of breakers and you can use 80% of that , that would be 208. 320- 208 still leaves you 112. So it looks like you are in good shape. Paul

I think my fellow professional electricians will agree: This WHOLE post is wrong. Please disregard all of it.